664441981 has 4 divisors (see below), whose sum is σ = 759362272. Its totient is φ = 569521692.

The previous prime is 664441931. The next prime is 664442021. The reversal of 664441981 is 189144466.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 664441981 - 2¹⁹ = 663917693 is a prime.

It is a super-2 number, since 2×664441981² = 882966292230408722, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (664441901) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 47460135 + ... + 47460148.

It is an arithmetic number, because the mean of its divisors is an integer number (189840568).

Almost surely, 2^664441981 is an apocalyptic number.

It is an amenable number.

664441981 is a deficient number, since it is larger than the sum of its proper divisors (94920291).

664441981 is an equidigital number, since it uses as much as digits as its factorization.

664441981 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 94920290.

The product of its digits is 165888, while the sum is 43.

The square root of 664441981 is about 25776.7721214275. The cubic root of 664441981 is about 872.6076608718.

The spelling of 664441981 in words is "six hundred sixty-four million, four hundred forty-one thousand, nine hundred eighty-one".